The use of specialized ink formulation to form thick films having various functions on suitable substrates in the construction of multilayer circuits is known. We have developed medium and high value thick film resistor inks based on indium oxide and containing magnesium oxide as a temperature coefficient of resistance modifier. These inks and their preparation are disclosed in our copending U.S. patent application, Ser. No. 280,934, filed July 6, 1981, now U.S. Pat. No. 4,380,750, issued Apr. 19, 1983 the disclosure of which is incorporated herein by reference.
The subject inks are compatible with conventional substrates and are particularly suited for use with porcelain-coated metal substrate for circuit fabrication which are disclosed in Hang et al., U.S. Pat. No. 4,256,796, issued Mar. 17, 1981, the disclosure of which is incorporated herein by reference. The subject inks are also compatible with inks having various other functions which are formulated for use on the Hang et al. substrates.
The subject inks are medium and high value resistor inks, i.e. they are formulated to have resistance values of from 500 to one million ohms per square. The subject inks are characterized by a stable temperature coefficient of resistance (TCR) at both ends of this range.